Language &
Consciousness
Lesson 27
Lateralization of Function
Hemispheres specialized
 process information differently
 L: “analytic” vs R: “holistic”
 information shared via commissures
 Language
 meaning  Left hemisphere
 emotional content  Right hemisphere ~

Lateralization: Language
Evidence from stroke victims
 Left hemi. damage
 aphasias
 paralysis: right side
 Right hemi. damage
 no aphasias
 paralysis: left side
 Females less lateralization
 unilateral lesion  less aphasia ~

Language & Consciousness

Experiment
 put one hemisphere asleep
• Sodium amytal
Right hemisphere asleep
 object in right hand (behind back)
 can verbally ID
 Left hemisphere asleep
 In R. hand  no verbal memory
 In L. hand  can ID by touch ~

Mind/Brain Relationship
Monism
 mind product of brain function
 Dualsim
 fundamentally different and
separate
 Split brain  2 minds?
 commissurotomy
 Monism?
 Dualism? ~

Split Brain Research
Commissurotomy
 sever corpus callosum
 Humans
 treatment of severe epilepsy
 Animals
 also sever optic chiasm
 only ipsilateral visual inputs
 No communication b/n hemispheres ~

Animal Research
Myers & Sperry - Nobel prize
 2 consciousnesses in 1 body?
 Cats & monkeys
 cut corpus callosum & optic chiasm
 Completely lateralized visual input
 left eye  left hemi only
 right eye  right hemi only
 Do hemispheres have different
experiences? ~

Cat Neuroanatomy
CC
Discrimination Training
Left eye open
 Discrimination training
 triangle  press button  reward
 circle  press button  no reward
 After learned cover left eye
 no longer performs task
 information not available to right
hemi
 1 hemi learned association
 other one did not ~

Discrimination Training
Differential training
 left: triangle  reward
 right: circle  reward
 no pressing for non-rewarded shape
 Hemispheres learned different things
 separate consciousnesses? ~

Human Split-Brain Research
Commissurotomy  epilepsy tx
 optic chiasm intact
 no apparent deficits
 contralateral visual inputs
 Lateralized visual input
 Tachistoscope or T-scope
 < 200 msec
 info to 1 hemisphere ~

Human Split-Brain Research
Discrimination training
 same as animals
 Verbal identification of objects
 visual
 tactile
 Other interesting phenomenon
 L & R competition
 and more ~

LVF
L
Speech
Body
RVF
Mute
Body
R
LVF
Normal subject
CC intact

What did you see?
~
RVF
LVF
L
Speech
RVF
R
LVF
Normal subject

What did you see?

info to Left via CC ~
RVF
LVF
L
RVF
Speech
Mute
CC
R
LVF
RVF
Split-brain
CC cut

What did you see?
~
CC
LVF
L
Speech
RVF
R
LVF
RVF
Split-brain

What did you see?
CC
~
LVF
L
RVF
Speech
Mute
CC
R
I.D. by R. Hemisphere
L. Hemi  no knowledge of key
 How can R. hemi identify?
 reach into bag w/ L. hand
 I.D. the key
 R. hand cannot I.D. by touch ~

LVF
RVF
Split-brain
L
Speech
Body
Mute
Body
R
Paul - Mr. P.S.
Split-brain patient
 R. & L. hemi language
 spell w/ L. hand using scrabble letters
 “I know it wasn’t me that did that.”
 Like Clive Wearing’s writing
 His explanation: “unconscious writing”
 Simultaneous lateralized inputs? ~

LVF
L
RVF
Speech
Mute
CC
R
Paul - Mr. P.S.
Point to the object best related to
what you see
 R. hand  chicken
 L. hand  shovel
 “I saw a claw and I picked the
chicken, …
and you have to clean out the
chicken shed with a shovel. “
 Confabulation ~

Paul - Mr. P.S.
T-scope to ask questions
 Who is your girlfriend?
 R & L  same answer
 Career choice: I want to be a _____.
 L. hemi.  doctor
 R. hemi  race car driver
 2 consciousnesses in 1 body? ~

The Nature of Consciousness
Split-brain  split consciousness?
 Monism vs. Dualism
 How do you split a nonphysical entity?
 supports monist view
 Brain & Behavior
mental states  physiological states ~
